prlimit(1)

prlimit(1) is a new util that will be available in util-linux-2.21 (now -rc1). This new util is very nice and flexible command line interface to prlimit(2) Linux syscall (supported since Linux 2.6.36).

prlimit(1) allows to get or set one or more process resource limits for given PID. When a command is given instead of PID, prlimit(1) will run this command with the given resources.

The output is flexible like output from lsblk(8) or findmnt(8). You can define the output columns, use parsable output etc.

See the default output:

  $ prlimit --pid $$
  RESOURCE   DESCRIPTION                             SOFT      HARD UNITS
  AS         address space limit                unlimited unlimited bytes
  CORE       max core file size                         0 unlimited blocks
  CPU        CPU time                           unlimited unlimited seconds
  DATA       max data size                      unlimited unlimited bytes
  FSIZE      max file size                      unlimited unlimited blocks
  LOCKS      max number of file locks held      unlimited unlimited
  MEMLOCK    max locked-in-memory address space     65536     65536 bytes
  MSGQUEUE   max bytes in POSIX mqueues            819200    819200 bytes
  NICE       max nice prio allowed to raise             0         0
  NOFILE     max number of open files                1024      4096
  NPROC      max number of processes                 1024     62809
  RSS        max resident set size              unlimited unlimited pages
  RTPRIO     max real-time priority                     0         0
  RTTIME     timeout for real-time tasks        unlimited unlimited microsecs
  SIGPENDING max number of pending signals          62809     62809
  STACK      max stack size                       8388608 unlimited bytes

or redefine the output and ask for max number of open files only:

  $ prlimit  --nofile --output RESOURCE,SOFT,HARD --pid $$
  RESOURCE SOFT HARD
  NOFILE   1024 4096

and now let's modify the soft limit of maximal core file size and maximal number of open files:

  $ prlimit --core=1000000: --nofile=100: --pid $$

the notation used for the limits is:

  soft:hard    specify both limits
  soft:        specify only the soft limit
  :hard        specify only the hard limit
  value        specify both soft and hard limits to the same value

and check the result:

  $ prlimit  --nofile --core --pid $$
  RESOURCE DESCRIPTION                 SOFT      HARD UNITS
  NOFILE   max number of open files     100      1024
  CORE     max core file size       1000000 unlimited blocks

and revert the core file soft limit:

  $ prlimit --core=unlimited: --pid $$

  $ prlimit --core --pid $$
  RESOURCE DESCRIPTION             SOFT      HARD UNITS
  CORE     max core file size unlimited unlimited blocks

Do you want to restrict CPU time for given command (sort(1) in this example):

   $ prlimit --cpu=10 sort -u hugefile

I think prlimit(1) is much better than the shell built-in command ulimit.

Thanks to Davidlohr Bueso who found time to implement prlimit(1) for util-linux 2.21.

-- In memory of Dennis M. Ritchie

frustrating gnome-control-center network

The "gnome-control-center network" is pretty incomplete application. Unfortunately, this application is called by gnome-shell if you want to modify your network settings. And all this is default in Fedora-16. Grrrr...

The most stupid thing is that you cannot configure wireless connections if your wireless is disabled. And if you enable wireless then you will be affected by your broken configuration...

Fortunately, old good nm-connection-editor works as expected. So, all you need is to kick off the idiotic network stuff from gnome-shell and start old good Network Manager Applet:

 mv /usr/share/gnome-shell/js/ui/status/network.js \
       /usr/share/gnome-shell/js/ui/status/network.disabled

and restart gnome-shell (command 'r').

gnome-shell is not so bad

It seems that I will be able to use GNOME 3. I love the minimalism provided by gnome-shell. It's gnome, so it's tricky to fully customize the desktop, but it's possible.

My requirements:

• no animations (gnome "switch workspace" is pure hell...)
• tagging -- at least for terminal (fluxbox supports this for arbitrary application, gnome has at least gnome-terminal with tabs)
• minimalistic windows decoration
• no window title for maximized windows
• tiny window title for normal and modal windows
• no max/min/close buttons for windows (I have keyboard...)
• pretty visible focused window (e.g. green border)
  
• only one tiny panel
• WM has to remember workspace for applications (e.g. firefox = 2nd workspace)

We all love screenshots, right? ;-) My old good fluxbox here, and the "same" with GNOME 3 is here.

The first step is to install some gnome-shell extensions:

• Native Window Placement Extension
• Auto move windows extension
• Disable Window Animation Extension
• Remove User Name Extension
• windowNavigator Extension

The next steps is to make windows decorations more minimalistic. This step is more tricky, because you have to modify window manager theme (for more details see gnome bug 594879). My theme is available at my home page.

The next step is to customize desktop files for some applications, for example I want to start gnome-terminal with --hide-menubar option, so

cp /usr/share/applications/gnome-terminal.desktop \
   ~/.local/share/applications/myterm.desktop

and modify Exec and Name entries in the file. Then you can add the application to your gnome-shell Favorites.

The last step is to customize keyboard shortcuts, this is simple (see "keyboard" in gnome-control center).

Note than many things like info about CPU temperature does not have to waste any place on your desktop. IMHO it's better to use keyboard shortcuts and print necessary information to the screen on demand. For example I use osd_cat:

#!/bin/bash

BATT=$(acpitool -b | awk -F ':' '/Battery/ { print $2 }' | sed 's/ //')
AC=$(acpitool -a | awk -F ':' '/AC/ { print $2 }' | sed 's/ //g')
TEMPE=$(sensors | awk '/temp/ { print $2 }' | sed 's/ //g')
FAN=$(sensors | awk '/fan/ { print $2 }'  | sed 's/ //g')

(printf "    Battery: %-20s\n" "$BATT"
printf "         AC: %-20s\n" "$AC"
printf "Temperature: %-20s \n" "$TEMPE"
printf "        Fan: %-20s\n" "$FAN") | osd_cat --delay 4 --pos bottom      \
                                                          --align right --offset 45 --indent 10 \
                                                          --color green --font "-misc-fixed-*-*-*-*-20-*-*-*-*-*-*-*"